Re: Fw: Re: 2.6.17-rc1-mm1 - detects buggy TSC on GEODE

Re: Fw: Re: 2.6.17-rc1-mm1 - detects buggy TSC on GEODE

[Jordan Crouse]

On 07/04/06 17:41 -0700, Andrew Morton wrote:
> 
> Sorry, I should have cc'ed you on this :(
 
No worries. 

> > > 1.   the new kernel is now detecting the buggy TSC on the GEODE-sc1100
> > > 2.    the bug is apparently correctable by passing 'idle=poll' on kernel 
> > > boot-line.

I am assuming that this is the problem where the TSC doesn't roll over
correctly on the SC1100 and SC1200.

> > John, does this mean that enable-tsc-for-amd-geode-gx-lx.patch is only safe
> > to merge after all your time-management patches have gone in?

If that is the case, then the enable-tsc-for-amd-geode-gx-lx.patch is still
safe since the TSC on the GX and LX doesn't have that same problem.

For what its worth, we used to have a fix for the TSC issue back
in the 2.4 days that looked something like this:

#ifdef CONFIG_GEODE_SC1200
#define rdtsc(low,high) \
	__asm__ __volatile__("rdtsc" : "=a" (low), "=d" (high)); \
	if ((unsigned long) low > 0xFFFFFFFC) high--
#else
#define rdtsc(low,high) \
	__asm__ __volatile__("rdtsc" : "=a" (low), "=d" (high))
#endif

That seemed to work, but it is ugly, and I didn't bring it forward
when we moved to 2.6.  Perhaps we can revive it if there are SC1100/SC1200
users who need it.

Thanks,
Jordan

-- 
Jordan Crouse
Senior Linux Engineer
AMD - Personal Connectivity Solutions Group
<www.amd.com/embeddedprocessors>